(1) Field of the Invention
The present invention relates generally to a thermostable mannitol dehydrogenase from Thermotoga maritima. Specifically, the present invention relates to the use of this enzyme on a bioreactor electrode in a bioreactor system to produce mannitol from glucose or fructose.
(2) Description of the Related Art
Currently, 50,000 tons/year of mannitol are produced by hydrogenation of a 50% fructose/50% glucose syrup at high pressures and temperatures using a Raney nickel catalyst. The fructose/glucose syrup is converted to a 30% mannitol-70% sorbitol mixture from which mannitol is purified by low-temperature crystallization. Developing a new, simplified, enzyme-catalyzed process for mannitol production could lower product costs. By starting from 100% glucose, it would increase the chemical yield (one mole mannitol produced per mole of glucose), and lower the downstream processing costs by eliminating the crystallization step. It would also allow mannitol to be called a natural product.
Mannitol is used as a low-caloric and low-cariogenic sweetener (in particular in diabetic foodstuffs), as a pharmaceutical formulating agent (e.g., used as a diuretic in the manufacture of intravenous fluids and tablets, in dental hygiene products, and as a low reactivity drug filler), as a specialty chemical, and in plastic manufacturing. SpecChem Online estimates the global market for mannitol to be about $28 million (www.specchemonline.com, Sugaring the pill, Oct. 21, 2004).
While the related art teaches mannitol production, there still exists a need for an improved method of producing mannitol.